Multiple packer distribution valve and method



March 17, i9? D. L. FARLEY ET AL 3,500,9H

MULTLE ACKER DISTRIBUTION VALVE AND METoD Filed May 18. 1967 INVENTORSHAROD f2. PAA-SWW@ @ID lB a+;

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:Ill Il Avit o a a a g 5 United States Patent O 3,500,911 MULTIPLEPACKER DISTRIBUTION VALVE AND METHOD David L. Farley and Harold R.Armstrong, Duncan,

Okla., assiguors to Halliburton Company, Duncan,

Okla., a corporation of Delaware Filed May 18, 1967, Ser. No. 639,461Int. Cl. E21b .i3/124, 47/06 U.S. Cl. 166-250 16 Claims ABSTRACT OF THEDISCLOSURE In drill stem testing of wells, the formation to be tested issealed from the hydrostatic pressure of fluid in the well. This seal isprovided by a pair of expandable packers positioned above the formation.The packers are spaced apart in the tubing string and a port in the subconnecting the packers establishes fluid communication between theinterior and exterior of the sub. A valve opens and closes the port inresponse to fluid pressure acting on the valve element. The valve openswhile the string is being run to the depth of the formation in responseto the hydrostatic pressure of the well fluid. After the packers havebeen expanded, the fluid pressure in the annulus below the upper packerdrops as fluid bleeds through the port into the interior of the sub. Thevalve closes when the pressure reaches a certain minimum value. Thehydrostatic pressure at the depth of the formation is determined and thevalve is adjusted to close ata predetermined lower pressure to establisha pressure differential across the upper packer and pressuredifferential across the lower packer, so that the hydrostatic load isdistributed between the packers.

CROSS REFERENCE TO RELATED APPLICATION This invention is in somerespects an improvement over the invention disclosed and claimed inOlson et al. application, entitled Pressure Regulating Valve AssemblyBetween Open Hole Packers and Method, Ser. No. 639,384, filed May 1S,1967, now Patent No. 3,459,264.

BACKGROUND OF THE INVENTION This invention relates to well apparatus andmore particularly to method and apparatus for preventing the leakage offluid around well packers in open hole drill stem testing.

In drill stem testing, it is common practice to assemble a tester tooland a packer on the lower end of a drill string and to lower the stringinto the well bore. At the appropriate depth, the packer is expanded toengage the wall of the well bore thereby sealing off the formation belowthe packer. A valve in the tool then may be operated to obtain a test ofpressure and fluid conditions in the isolated formation.

If the formation being tested is at a considerable depth, the pressuredifferential across the packer due to hydrostatic pressure of the fluidin the bore hole may be suf'llciently great to cause leakage around thepacker.

The reliability of productivity evaluations based on drill stem testingdepends among other factors, on the accuracy of pressure and flowmeasurements of the isolated formation. If error is introduced throughthe leakage of pressure fluid around the packer, the values of pressureand flow rate may cause inaccurate production rates and othercharacteristics of the formation to be estimated.

Attempts have been made to utilize several packers in a string forsealing a formation from drilling mud in the annulus above theformation. For example, Roberts Patent No. 2,959,225, issued Nov. 8,1960, discloses an air or gas drilling system in which two packers in atubing string are expanded into sealing relation with the bore hole.Drilling mud fills the annulus above the packers, while air or gas ispumped down the drilling string to cool the bit and to carry away thecuttings. Roberts further discloses a pressure-proportioning device forequalizing the hydrostatic load across the packers, but the deviceoperates in response to a fixed ratio of pressure above the upper packerto pressure in the space between the packers. The pressure differentialacross either the upper or lower packer may be so great that leakagewill occur around the packers, although the pressure ratio is properlycontrolled by the device. This problem is particularly significant indeep wells where high hydrostatic pressures are encountered.

Accordingly, it is an object of this invention to provide a method andapparatus for improving the accuracy of drill stem testing of open holeformations.

It is a further object of this invention to provide a method andapparatus eliminating leakage of fluid around a packer due to highhydrostatic pressure on the packer.

Another object of this invention is to provide a meth- Od and apparatusfor effectively isolating a formation from the hydrostatic pressure ofwell uids while conducting formation tests.

SUMMARY OF THE INVENTION These objects are accomplished in accordancewith a preferred embodiment of the invention by providing a pair ofpackers spaced apart in the drill string. A pressure distribution valveis positioned in the string between the two packers. The distributionvalve has a port located between the packers and communicating betweenthe interior and exterior of the string. Fluid flow through the port iscontrolled by a valve element which is spring biased toward a closedposition, but has a fluid reaction surface urging the valve elementtoward an open position. An anchor positioned in the string below thelower packer allows fluid to flow into the interior of the string. Acentral passage in the string provides fluid communication between theanchor and the distribution valve.

While the string is being run in the bore hole, hydrostatic pressure ofthe fluid in the bore hole communicates through the anchor to theinterior of the string where the hydrostatic pressure acts on thereaction surface of the distribution valve, The spring in thedistribution valve allows the valve element to open the port when thehydrostatic pressure at the depth of the valve is at a selected valuebelow the hydrostatic pressure at the depth where the packers are to beset. When the packers reach the depth of the formation, the packers areexpanded into engagement with the wall of the open bore hole. Thenterior of the string is then isolated from the pressure of the wellfluid above the upper packer. The distribution valve remains open tobleed fluid from the space between the upper and lower packers while thepackers are being expanded and until the pressure reaches the selectedvalue. The valve then closes, isolating the space between the upper andlower packers, and as a result, the pressure differential across theupper packer and across the lower packer is sufliciently low to avoidyleakage around the packers into the test Zone.

DESCRIPTION OF rl'I-IE DRAWINGS This preferred embodiment is illustratedin the accompanying drawings, in which:

FIG. 1A is a schematic View in elevation of the upper portion of a teststring made up in accordance with this invention and run in a bore hole;

FIG. 1B is a schematic view of the lower portion of the test string asin FIG. 1A; and

FIG. 2 is a cross sectional view of a pressure relief valve.

3 DESCRIPTION OF PREFERRED EMBODIMENT Formation testing techniques havebeen developed to determine the potential productivity of a subsurfaceformation. A tubing string or drill string is positioned in a bore holethat is drilled into the formation that is to be tested. A packer on thestring isolates the formation from hydrostatic pressure of drilling mudin the annulus and uid from the formation is allowed to flow into thedrill string under simulated production conditions. The test isconducted for a short period of time, and While the fluid is owing fromthe formation into the drill string, the pressure of the formation fluidand the ow rate in the drill string are measured. From thesemeasurements, the potential productivity of the formation may becalculated.

In FIGS. 1A and 1B, information testing apparatus H is secured in aconventional manner to the lower end of a drill string 4. A bore hole 6extends through an overlying formation 8, and the lower end of theapparatus 2 is positioned at the bottom 10 of the bore hole. Theformation 12 at the bottom of the bore hole is the formation that is tobe tested.

The formation testing apparatus includes a tester tool 14 which issecured to the string 4 by a conventional coupling 16. The purpose ofthe tester tool is to control the flow of fluid from an isolatedformation while the test is being conducted. The tester valve is usuallyoperated by axial and rotational movement of the drill string. Examplesof well tester tools which may be employed for the tool 14 are thosedisclosed in Schwegman Patent No. 2,740,479, and Chisholm Patent No.3,105,553.

Below the tester 14, conventional ewell tools, such as Bourdon tubepressure recorder for measuring the pressure on the outside of the tool,a jar 22, and, at the bottom of the hole `6, a flush joint anchor 24 maybe ineluded in the string. Below the anchor 24 is a Bourdon tubepressure recorder 26.

The jar 22 is a conventional well tool for applying a sharp axial blowto the string to break loose a tool, such as a packer, that may havebecome stuck in the well bore. The anchor 24 is merely a thick wall pipehaving a plurality of small perforations through which well fluid flowsto the interior of the string. The pressure recorders 20 and 26 areconventional devices utilizing a Bourdon tube with a stylus attached tothe movable end of the tube to record on a moving chart the localpressure as a function of time.

The apparatus 2, which includes the tester tool 14, the jar 22, thepressure recorders 20 and 26, and the anchor 24 are merely illustrativeof tools used in a typical testing string. The invention is concernedwith establishing a seal which isolates the formation being tested fromthe hydrostatic pressure in a well bore while the test is beingconducted. Thus, various testing tools and conventional auxiliary toolsmay be assembled in a testing string in combination with the improvedpacker assembly of this invention.

The packer assembly 28 of this invention is positioned in the stringbetween the hydraulic jar 22 and the anchor 24. The packer assembly 28separates the formation 12 at the bottom of the bore hole 6 from theannulus surrounding the tubing string above the packer assembly 2S. Inconventional practice, the bore hole is filled with drilling mud inorder to contain the formation fluid within the formation and to preventthe rapid release of pressure that might be encountered in drilling.Often the drilling mud is weighted with additives and if the testing iscarried out at substantial depths, the hydrostatic pressure of thedrilling mud may be extremely high. The packer assembly 28 serves toisolate the formation 12 that is to be tested from this hydrostaticpressure.

Usually a tester tool has associated with it a bypass valve to equalizepressure across the packers before they are collapsed after completionof the test. The ports 18 correspond to the bypass ports 64 of Chisholm,No.

3,105,553, for example. A safety joint 30 is shown schematically in FIG.1A. This tool permits the drill pipe and testing tools to be detachedfrom the packer and anchor in the event that one or both become stuck inthe well. The safety joint 30- consists of two parts which are unscrewedby a series of rotational and vertical movements of the drill pipe. Thistool also has a bypass valve indicated at 32 which acts as an auxiliaryto the bypass in the tester tool 14.

An upper packer 34 includes expanding shoe assemblies and a resilientexpandable packer ring 36. The assembly 28 also includes a lower packer38 similar to the packer 34 and including a resilient expandable packerring 40. Secured between these packers is a pressure distribution valve42.

The packers 34 and 38 should be retrievable and may be of anyconventional construction that would not interfere with the operation ofthe tester 14, but preferably, the packers are of the compression typeas disclosed in Morrisett Patent No. 2,808,889.

The distribution valve 42 includes a top adapter 44 and a bottom adapter46. The adapters 44 and 46 have internal and external threaded portions,respectively, for being rigidly secured to the adjacent packers 34 and38. The adapters 44 and 46 have a continuous central passage 48 whichextends from one end of the valve to the other. A mandrel 50 is mountedin the central passage 48 and is movable longitudinally relative to theadapters 44 and 46. The mandrel 50 has an external flange 52. Theexternal diameter of the mandrel 50 above the ange 52 is less than theexternal diameter of the mandrel below the flange 52, as viewed in FIG.2. A pair of O-ring seals 54 at the upper end of the mandrel 50 preventthe leakage of Huid between the mandrel and the upper adapter 44. O-ringseals 56 and 58 are also provided at the lower end of the mandrel 50.

Since the exposed cross sectional area at the lower end of the mandrel50 is larger than the cross sectional area at the upper end of themandrel 50, fluid pressure in the passage 48 tends to urge the mandrel50 upwardly. Movement of the mandrel, however, is resisted by a coilspring 60 in the space between the mandrel and the lower adapter 46. Aspacer ring 62 is inserted between the lower end of the spring 60 andthe flange 52. Preferably, the coil spring 60 has a linear spring rate,so that the spring force increases in proportion to the axialcornpression of the spring. The spacer ring 62 imposes an initialcompression of the spring, thereby increasing the spring biasing forceon the mandrel which must be overcome by the pressure differentialacting on the mandrel to move the flange 52 upwardly off its seat. Theamount of precompression of the spring 60 may be varied by replacing thespacer ring 62 with another spacer ring having a different axial length,or the ring may be entirely removed to allow the lo'wer end of thespring 60 to engage the ange 52.

The lower adapter 46 has a plurality of radial ports 64. When themandrel 50 is at its lowermost position, as shown in FIG. 2, the ports64 are sealed from the interior passage 48 by the Orings 56 and 58. Whenthe mandrel 50 is displaced upwardly, relative to the lower adapter 46,a sufficient distance for the seal rings 58 to be positioned above theports 64, then the interior passage 48 is in communication with theexterior of the valve 42 through the ports 64.

Due to the difference in cross sectional area of the lower end of themandrel 50 relative to the upper end of the mandrel 50, fluid pressurein the passage 48 tends to move the mandrel 50 upwardly in opposition tothe force of the spring 60. By selecting appropriate springs 60 orspacer rings 62, the valve 42 can be arranged to open the port 64 at thedesired iluid pressure in the passage 48 and to close the valve againwhen the pressure drops below a selected pressure. Although the valve42, shown in FIG. 2, is preferred, other valves which operate to allowcommunication through the valve body when the pressure at the valve 42exceeds a predetermined value may be used.

In operation, the string is made up as in FIG. 1A and FIG. 1B, with thepackers 34 and 38 in a collapsed condition. The string is lowered intothe bore hole on the drill pipe with the tester valve in the tool 14closed to prevent entry of well fluid into the drill pipe. The bypassports 18 and 32 are open to allow circulation of fluid from the anchor24 to the tester tool 14. When the string reaches the bottom of the-bore hole 6, the packers 34 and 38 are expanded in accordance withconventional practice into sealing relation with the yadjacent wall ofthe bore hole 6.

Since the bore hole is filled with drilling mud, the hydrostaticpressure of the mud gradually increases as the string is being loweredin the bore hole. This pressure is applied to the mandrel 50 through theanchor 24. The mandrel 50 in the valve 42 opens the ports 64 when thehydrostatic pressure of the drilling much acting on the mandrel exceedsa predetermine value. The value selected for opening the ports 64 ispreferably below the measured or calculated hydrostatic pressure of thedrilling mud at the bottom of the bore hole. Therefore, in lowering thedrill string to the bottom of the bore hole, the uid pressure in thepassage 48 causes the mandrel 50 to be displaced upwardly when the depthof the tool is suicient to impose the required hydrostatic pressure onthe mandrel. The ports 64 remain open, while the packers 34 and 38 arebeing expanded, so that the fluid pressures in the annulus above theupper packer 34, between the packers, and below the lower packer 38, areall approximately the same, allowing for differences due to hydrostatichead.

When the packers have been expanded, the bypass valve in the safetyjoint 30 and the bypass port 18 in the tester are closed and the testervalve is opened. The formation 12 Ibelow the lower packer 38 is relievedof the hydrostatic pressure of the well uid, -and is exposed through theopen tester valve to the atmospheric pressure in the empty drill pipe.As soon as the tester valve opens, the pressure in the passage 48 of thedistribution valve 42 is reduced and uid from the annulus flows throughthe ports 64 into the passage 48. This ow continues to reduce thepressure in the annulus until such time as the pressure in the passage48 has been reduced to the pressure at which the mandrel 50 is displacedby the spring 60 to the closed position.

The pressure below the lower packer 38 continues to be reduced while thetester valve is open, since well fluid flows through the anchor 24 andupwardly through the passage 48 and into the drill pipe above the tester14. At this time, the upper packer 34 is exposed from above to thehydrostatic pressure of the well fluid and the lower side of the upperpacker is exposed to the intermediate pressure established by thedistribution valve 42. The lower packer 38 is exposed to theintermediate pressure on its upper side and to a lower pressure on itslower side, depending upon the pressure of fluids in the formation 12.Thus, the pressure differential across the upper packer is substantiallyless than the total differential across the entire packer assembly 28.

At the end of the test, the tester valve is closed and the pressure isequalized across the packers by opening the ports 32 and 18. The packers34 and 38 are then collapsed and the drill string may be raised from thebore hole.

The distribution valve 42 not only establishes a predetermineddifferential of pressure across the upper and lower packers, but alsoovercomes the danger of fracturing the formation or destroying the upperpacker seal by hydraulic pressure of fluid trapped `between the packers34 and 38 while they are being expanded. For example, if the upperpacker 34 was expanded first to seal against the bore hole wall, rapidexpansion of the lower packer 38 may produce pressure surges which woulddestroy the upper packer seal. The ports 64 in the sub between thepackers, relieve any excessive increases in pressure in this zone. Bydistributing the pressure across two or more packers, the pressuredifferential across each packer s substantially reduced, so that thereis less tendency for the well fluid to communicate through a verticallyfractured formation into the bottom of the well bore where it would flowinto the test string.

The operation of the method and apparatus of this invention have beenverified by field tests `with a pressure recorder inserted in the stringbetween the upper and lower packers to record the pressure in theannulus. During the field test, the processure recorder indicated thatwhile the packers were expanding, the pressure in the annular spacebetween the packers exceeded the hydrostatic pressure. This increase inpressure was due to the inflation or expansion of the packers. Anexcessive rise in pressure can fracture or destroy the upper packerseal.

As an example, if a test is being taken in a bore hole having a depth of20,000 ft. with drilling mud having a density of 10.5 lbs. per gallon,the hydrostatic mud pressure at the bottom of the hole would beapproximately 10,900 p.s.i. It is anticipated that the maximum pressurein the formation 12 at the bottom of the hole is 5000 p.s.i. A watercushion of 8000 ft. is run inside the test string creating a backpressure of 3400 p.s.i. The packers 34 and 38 are positioned in thestring as shown in FIGS. 1A and 1B, with the distribution valve 42adjusted to open at a pressure in the passage 48 of 7000 p.s.i. As thestring is being lowered in the bore hole, the valve 42 opens at a depthcorresponding to a hydrostatic pressure of approximately 7000 p.s.i. Thevalve remains open while the packers are being expanded. After thebypass ports have Ibeen closed, and the tester valve 16 has been opened,the pressure in the annular space between the packers drops from 10,900p.s.i. to approximately 7000 p.s.i. At this pressure, the mandrel S0closes the ports 64, trapping fluid in the annular space between thepackers at a pressure of approximately 7000 p.s.i. Consequently, thereis a differential of about 3900 p.s.i. across the upper packer 34 andbetween 2000 p.s.i. and 3600 p.s.i. across the lower packer 38. Thedifferential pressure across each packer is considerably less than the5900 p.s.i. differential that would exist if a single packer, were used.

While this invention has been illustrated and described in a preferredembodiment, it is recognized that variations and changes may be madetherein without departing from the invention as set forth in the claims.

We claim:

1. In a drill string of the type having means for establishing atemporary seal in the annulus between said string and the wall of a borehole in which the drill string is run, said seal extending around theperiphery of said drill string to prevent ow vertically through theannulus, said seal comprising:

an upper packer ring and a lower packer ring on said drill string, meansfor selectively expanding said packer rings radially relative to saidstring,

said string including tubing having a central passage extendingcontinuously from a point above said seal to a point below said seal andremaining in continuous communication with said annulus below said seal,said tubing having a port communicating between said central passage andsaid annulus, said port being between said upper and lower packer rings,

a valve element in said tubing and movable to open and close said port,said valve element having a pair of opposed fluid reaction surfaces ofdifferent areas, the larger reaction surface urging said valve elementfrom said closed position toward said open position in response to fluidpressure in said tubing acting on said surface, both of said reactionsurfaces being positioned in said tubing central passage, and springmeans biasing said valve element toward said closed position, wherebysaid valve element is opened when the hydrostatic pressure on said fluidreaction surface exceeds a predetermined minimum pressure to relievefluid pressure in the annulus between said packer rings through saidport while said packer rings are being expanded and until apredetermined pressure differential is established across said upperpacker.

2. Apparatus according to claim 1 wherein the biasing force of saidspring means is adjustable.

3. Apparatus according to claim 1 wherein said drill string includesconduit means therein extending between said central passage and the topof said string, and tester valve means for selectively controlling uidflow between said conduit means and said central passage. wherebyopening said tester valve means after said packer rings are expandedisolates the central passage from hydrostatic pressure in the annulusabove said upper packer.

4. Apparatus according to claim 1 wherein said fluid reaction surface issealed from exposure to fluid in said port when said valve is in saidclosed position.

5. Well apparatus for establishing a temporary seal in a bore hole abovea formation that is to be tested cornprising tubing having a centralpassage therethrough, an upper expandable packer, a lower expandablepacker, said passage communicating with the exterior of said tubingbelow said lower packer, said tubing having a port between said packersextending through the wall of said tubing and communicating with saidcentral passage, valve means including a valve element movable to openand close said port, said valve element having a fluid reaction surfacein position for moving sadi element to said open position in response tofiuid pressure acting on said reaction surface, said reaction surfacebeing exposed to fluid in said passage and sealed from exposure to fluidin said port when said valve element is in said closed position, and

means for biasing said valve element toward said closed position,whereby fluid pressure bleeds through said port until the pressure inthe interior of the tubing is reduced below a predetermined minimumpressure, thereby establishing an intermediate pressure in the annularspace between said packers independently of the hydrostatic pressureabove said upper packer.

6. Well apparatus according to claim 5 wherein said valve element ismounted in said central passage and said Valve element is movableaxially without obstructing ow through said central passage.

7. Well apparatus according to claim S wherein said valve element is inthe form of a hollow mandrel, said mandrel being mounted coaxially insaid tubing for limited longitudinal movement relative to said tubing,said port being positioned intermediate the limits of said longitu- Ddinal movement, whereby said mandrel is movable in response to fluid insaid tubing.

8. Well apparatus according to claim 7 including shoulder means on saidmandrel` said biasing means including a coil spring aligned with saidshoulder means, and a spacer ring between said shoulder means and saidspring, whereby opening of said port can be adjusted by varying thelength of said ring.

9. The method of establishing in an open bore hole a predeterminedpressure differential across the upper packer of a pair of packers in atubing string comprising: determining the hydrostatic pressure in thebore hole at the depth of a selected formation, running said tubingstring down said bore hole, said tubing string including a pressuredistribution valve controlling fluid flow between the exterior of saidtubing string between said upper packer and the lower packer and theinterior of said tubing string,

opening said valve in response to a selected fiuid pressure within saidtubing string at a predetermined differential below the hydrostaticpressure at said selected formation, expanding said packers into sealingrelation with the wall of said bore hole above said formation,

reducing the fluid pressure in said tubing string adjacent said valve,closing said valve in response to fluid pressure in said tubing stringbelow said selected pressure, and maintaining said valve closed whilethe fluid pressure in said tubing string adjar cent said valve remainsbelow said selected pressure, whereby the pressure differential acrosseach of said packers is less than the total pressure differential acrossboth packers.

10. The method according to claim 9 wherein said valve closing occurs inresponse to absolute pressure in the annulus between said expandedpackers.

11. The method according to claim 9 wherein said tubing string interioris in uid communication with said selected formation, and wherein saidpressure reducing includes opening said tubing string interior toatmospheric pressure after expanding said packers, whereby predeterminedpressure differentials are established across the upper and lowerpackers.

12. A method of establishing a temporary seal while testing a formationin a bore hole containing fluid comprising:

running a tubing string in the hole with a pair of expandable packersspaced apart axially in said string, positioning said pair of packersabove said formation, said string including a valve communieatingbetween the exterior and interior of said string between said packers,

opening said valve in response to hydrostatic pressure above apredetermined pressure in said bore hole adjacent said valve, saidpredetermined pressure being intermediate the hydrostatic pressure insaid bore hole at said formation and fluid pressure in said formation,expanding said packers in sealing relation with said bore hole abovesaid formation,

reducing the fluid pressure in the interior of the string,

closing said valve in response to said reduction of fluid pressure belowsaid predetermined pressure, maintaining said valve closed whilepressure in said tubing string adjacent said valve remains below saidpredetermined pressure, and conducting productivity tests on saidformation, whereby said valve establishes an intermediate pressure inthe annular space between the upper and lower packers.

13. The method according to claim 12 wherein said valve closing occursat a predetermined pressure diferential with respect to the hydrostaticpressure directly above said upper packer.

14. The method according to claim 13 including determining saidformation fluid pressure and said hydrostatic uid pressure in said borehole, said predetermined pressure being at a selected pressuredifferential between said formation pressure and said hydrostaticpressure, whereby predetermined pressure differentials are achievedacross said upper packer and said lower packer which said tests arebeing conducted.

15. A valve assembly for controlling flow between the exterior and theinterior of tubing in a well comprising:

a tubular body having means at opposite ends thereof for connection ofsaid body in a tubing string, said body having a central bore extendingthroughout its length, said body having a substantially radial portextending through the wall and communicating between said bore and theexterior of said body,

a sleeve in said bore, said sleeve being movable longitudinally of saidbody and having a pair of opposed fluid reaction surfaces exposed`continuously to fluid pressure in said bore, said surfaces havingdifferent surface areas,

said sleeve being movable axially of said body in one direction forclosing said port, and in the opposite direction for uncovering saidport, the larger reaction surface being in position to urge said sleeveaxially to uncover said port, said sleeve having an outwardly projectingflange thereon, said flange having opposite faces, said body having apair of shoulders on opposite sides of said ange faces, and

spring means and an individual spacer ring interposed between one ofsaid shoulders and one of said faces, said spring means yieldably urgingsaid sleeve axially in said one direction toward a position closing saidport, the other of said body shoulders being position to be engaged bythe other of said ange faces when the sleeve is in said port closingposition, whereby fluid pressure in said bore greater than apredetermined value overcomes the force of said spring means to displacesaid sleeve longitudinally, thereby uncovering said port and whereby thelength of said spacer ring provides adjustment of the closing force ofsaid spring means.

16. The valve assembly according to claim 15, wherein said body has arecess in said bore, said sleeve extending over said recess and saidsleeve flange being received in said recess, said spring means and saidspacer being positioned in said recess, said port being spacedlongitudinally from said body recess, whereby said sleeve and saidspacer are confined in said recess by said sleeve.

References Cited UNITED STATES PATENTS Hux 166--148 Morris 166-151 XLewis 166-191 X Pittmann 166-224 Roberts 166-191 X Young 166-202 XBrandt 166-185 X Laird et al. 166-224 Baker et al 166-225 X Alexander166-224 X Hodges 166-224 X U.S. Cl. XR,

